Staphylococcus aureus is one of the most prominent of all bacterial pathogens. The continued emergence of drug resistance combined with its ability to produce virulence factors and biofilms has lead to increasing morbidity and mortality in both community and hospital settings. Biofilms produced by S. aureus are extremely difficult to eradicate and are the wearisome source of recalcitrant infection. Biofilms confer increased resistance to antimicrobial therapy and there is a clear need for the development of hovel antibiofilm therapies. The experimental focus of this proposal is to assess the potential of natural products extracted from white horehound (Marrubium vulgare L., Lamiaceae) for the treatment of biofilm-associated staphylococcal infection. White horehound is a wild herbaceous mint native to the Mediterranean. It is one of the most important medicinal plants used within the complementary and alternative medicine (CAM) framework of southern Italy. In particular, decoctions of the plant are topically applied for the treatment of several types of skin and soft tissue infection, many of which are related to staphylococcal infection. I have already established that crude ethanolic extracts of white horehound roots demonstrate remarkable activity in the disruption of established staphylococcal biofilms. The experimental component of this proposal is divided into four aims: 1) to fractionate and isolate bioactive compounds from white horehound;2) to assess the in vitro efficacy of white horehound compounds in the context of staphylococcal biofilms;3) to assess the in vitro cytotoxicity of active compounds;and 4) to assess the in vivo prophylactic and therapeutic efficacy of active compound(s) using murine models for catheter-associated staphylococcal biofilm infection. These aims will be addressed with bioassay-guided fractionation techniques, in which phytochemical methods (mechanism columns, HPLC, and LC/MS) will be combined with in vitro biofilm models. The cytotoxicity of active compounds will be assessed before the initiation of animal studies. A murine model will be used to assess the prophylactic capacity and therapeutic efficacy of these compounds in vivo. I believe that these experiments will ultimately lead to the identification of novel therapeutic agents for the prevention and treatment of staphylococcal catheter-associated biofilm infection. PUBLIC HEALTH RELEVANCE: Staphylococcus aureus causes devastating infections, and the current repertoire of antistaphylococcal drugs is insufficient. This proposal is aimed at investigating a popular plant-based traditional medicine for potential therapeutic applications in the prevention and treatment of biofilm infection.